Impact cratering redistributes geologic materials on up to global scales. On the Moon, cratering events contribute to the mixing of maria and the highlands. To better understand the role of impact ejecta in the redistribution of materials, we developed an analytical method to estimate the largest ejecta fragment sizes that could have been delivered to previous sample collection sites from selected primary impacts into lunar maria targets across the Moon. The ejecta fragments would not remain intact upon impact but would form secondary craters and be further eroded and mixed into the regolith. Here, we use maximum ejecta sizes as a proxy for the relative possible contributions of each assessed primary crater. All of the 45 primaries considered here (0.83–138 km in diameter) could potentially contribute sizable maria fragments to each landing site. The larger (>65 km diameter) and closer (<2,000 km distance) primaries resulted in the largest estimated fragment sizes (∼0.5–2.5 km), whereas the smaller (<65 km) and more distant (>2,000 km) primaries resulted in the smallest fragment sizes (up to ∼250 m). Depending on spatial proximity, both smaller and closer and larger and more distant primaries could also deliver relatively large (∼0.2–0.8 km) ejecta fragments. Our results provide context to understand how maria material may have become incorporated into distant surfaces and lunar sample locations.
Using observations from the Mars Climate Sounder (MCS) and images from the Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO), this study identifies a suppression of north polar ice cap expansion before the northern fall equinox (Ls ∼160°) in Martian Year 36 (MY36) compared to the same season in other years. This reduction coincides with an earlier-occurring tropical regional dust storm (Z storm). Simulations using the Mars Planetary Climate Model (PCM), along with a control experiment that excludes the Z storm, show an unusual decrease in atmospheric water vapor in the northern polar region, indicating that the ice cap anomaly is linked to dust storm–induced changes in atmospheric circulation and water transport. The Mars PCM simulations capture the key features of atmospheric temperature and water vapor changes during the Z storm period. To understand how the Z storm influenced polar water vapor, we conducted two PCM simulations for MY36: one representing the actual dust storm conditions and another representing a control experiment without the storm. Dynamical analysis showed that tropical dust activity excited anomalous planetary waves, which propagated poleward and affected the polar background circulation. As a result, circulation patterns in the lower polar atmosphere, including eastward zonal winds and meridional flows, were significantly disrupted, substantially reducing poleward water vapor transport to the northern polar region. These results provide new insights into the role of dust-related climate processes in modulating polar ice accumulation, contributing to a deeper understanding of the mechanisms driving long-term climate evolution on Mars.
We investigated the regolith parent rock (“protolith”) properties of Mare Tranquillitatis and Marius Hills on the Moon, utilizing lunar pit craters (“lua”) to contextualize observations of rock abundance and crater degradation. We discovered a significant difference in underlying materials: the region around the Tranquillitatis lua is characterized by a competent, dense, solidified basalt, whereas the region around the Marius Hills lua exhibits a more friable protolith, indicative of porous or vesicular volcanic deposits. These distinct protoliths directly influence rock evolution, with the Marius Hills region demonstrating higher initial rock excavation but also more rapid degradation of rocky ejecta and interiors, while the Mare Tranquillitatis region produces larger, more persistent blocks that resist fragmentation for longer periods. Consequently, the competent protolith of Mare Tranquillitatis makes its lua an ideal candidate for future lunar exploration missions, offering superior geotechnical integrity for potential subsurface habitats and enhanced protection from surface radiation and impact bombardment.
Venus' atmosphere layers between 80 and 130 km mark the transition between the superrotation and the day-to-night circulation regimes. Accurately modeling this layer is essential to better understand the planet's atmospheric dynamics. However, this region remains poorly constrained by observations, and its variability is not yet fully captured by current 3D models. Here we use the latest version of the Venus Planetary Climate Model (V-PCM), a ground-to-thermosphere global circulation model, to investigate possible scenarios relevant to future EnVision observations above the cloud tops. We focus on current data-model biases and provide a tentative interpretation of their origin. Benchmark simulations by Martinez et al. (2024, https://doi.org/10.1016/j.icarus.2024.116035) overestimate the nightside airglow emission by a factor of two and place the emission peak 5–7 km higher than observed. Furthermore, the emission distribution is not centered around midnight, but shifted to LT = 4h, likely due to a strong (100 m/s) zonal wind component below 105 km. We performed sensitivity tests on unconstrained parameters (e.g., gravity wave drag and eddy diffusion) to evaluate their impact on the dynamical structures. Results show that reducing non-orographic gravity wave forcing below 105 km weakens that superrotation wind component, and recenter the emission around midnight. However, the altitude bias appears linked to insufficient vertical transport in the model. These findings underline the need for future space missions capable of continuously monitoring mesospheric gravity waves and nightglow to better constrain their spatial and temporal variability and improve the representation of key dynamical processes in Venus' upper atmosphere.
NASA's InSight mission has provided an unprecedented snapshot of Mars' seismicity, despite data analysis challenges arising from low signal-to-noise ratios (SNR) and single-station constraints. High frequency (HF) events—the most common type—were initially assumed to propagate through shallow crustal layers. However, several impacts that occurred late in the mission provided independent distance constraints, indicating that HF event energy must have propagated through the mantle. We analyzed the full HF data set using an extended catalog and denoised waveforms derived with deep learning (DL) techniques. Using a DL ensemble, we picked phase arrivals on denoised envelopes and estimated SNR-dependent pick timing uncertainties based on the removed noise. We computed distances consistent with mantle paths using the latest Mars interior models, while the back azimuth remained inconclusive due to local resonance dominating the HF bandwidth. We compared and grouped HF recordings by their similarity and investigated how attenuation properties shape their envelopes. Additionally, we re-calibrated and assigned magnitudes for the extended catalog. Overall, we (re-)located 1,430 HF events clustered between epicentral distances of around 1,600–3,600 km, but without constraints on the back azimuth, their source region remains speculative. Based on spatiotemporal similarities, we attributed a subset of 1,357 events to a common source region and labeled them as swarm events. The analysis of envelope shape confirms and extends previous results of stratified attenuation properties. Swarm events, with magnitudes between 1.5 and 2.5, are cumulatively equivalent to a single magnitude 4 event and show a high -value and clear seasonal trends in seismicity.
Traveling waves in the Martian atmospheres play a crucial role in determining the weather and climate, particularly at mid-to-high latitudes. Previous observations have shown that these waves become prominent from early autumn to late winter in the northern hemisphere, influencing the dust cycle. However, their impact on the transport of dust and water ice clouds has not been studied quantitatively. Investigating the interaction between traveling waves and transport of such substances provides deeper insights into the climatology of Mars. In this study, we utilize data taken by the Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter. Observations reveal eastward-propagating waves during the northern autumn and winter, identified as Rossby waves. The results show that waves with a zonal wavenumber of 1 become prominent during this period and in this region. Moreover, there is a correlation among the periodic variations in temperature, dust, and water ice. The amplitudes of the temperature, dust, and water ice variations are roughly consistent with each other, suggesting that the variations are all driven by the meridional advection associated with the traveling waves. These findings suggest that traveling waves play a significant role in the transport of dust and water ice clouds on Mars.
Understanding the sources of hydration on Vesta's surface provides insights into water origins in the inner solar system. We estimated the hydration content across Vesta's surface using new calibrated Dawn VIR data. High content of hydration (up to 1,000 ppm) was observed in previously identified carbonaceous chondrite (CC)-rich regions. CC-poor areas consistently showed around 100 ppm of solar wind-induced hydration with no latitudinal dependence, likely due to Vesta's low surface temperatures and high axial tilt. Despite receiving less solar wind flux, Vesta's low-latitude surfaces exhibit higher hydration content than the Moon's, attributed to better hydration retention at lower temperatures (e.g., <∼280 K). At high latitudes (>∼80°) where the maximum daytime temperatures are less than ∼280 K, the Moon can effectively retain around four to five times hydration as that on Vesta, which is in great accordance with the greater solar wind fluence received by the Moon at its heliocentric distance. Our study suggested that the formation of water by solar wind implantation is ubiquitous on airless bodies in the solar system and that the retention of solar wind water is dominantly controlled by surface temperatures of these bodies.
Surface observations of Saturn's moon Titan revealed features characterized as dissected, elevated plateaus with high valley density known as labyrinth terrains. Of this terrain class, a subtype referred to as radial labyrinth is described as dome-shaped uplifts with radial channel patterns. Uplift of these radial labyrinths has previously been explained as cryomagmatic intrusions at the brittle–ductile transition zone. Here we propose an alternative hypothesis that crustal heterogeneities in Titan's upper clathrate crust introduce density differentials due to ethane-methane substitution, as ethane-rich liquids percolate into methane clathrate, inducing solid state flow and generating domal topography. This mechanism is analogous to salt tectonics on Earth and has similarly been evoked for dome formation on the dwarf planet Ceres. We show that the elevation and width of the observed radial labyrinths are consistent with domal uplift driven by a hydraulic head within the uppermost portion of Titan's crust, given a plausible set of elastic parameters for clathrate hydrates. Additionally, the insulating effect of clathrate, combined with partial mixing with water-ice, allows for sufficiently low viscosity for geologic flow on a relevant timescale: uplift of the domes could have occurred within the last billion years.
Pitted cones have been studied on Earth for at least two millennia, and they are often linked to an origin that requires H2O in some form. Identified on Mars half a century ago, pitted cones have been studied on the red planet with remote sensing data, and different formation models have been proposed based on terrestrial examples. In this work, we examine pitted cones on Mars that formed in patterns along the perimeter of circles, but have heretofore not been detailed in the literature. Pitted cones in these circular macrostructures are found in large quantities only in a small, ∼7,000 km2 region of Elysium Planitia, which has been dated to <10 Myr. We propose that these circular macrostructures follow the rims of buried impact craters, and that sediment-laden H2O and/or steam breached the surface where the most recent resurfacing is thinnest and therefore weakest, tracing these buried crater rims. Such a formation method is a mud volcano. Mud volcanoes typically require subsurface volatiles such as H2O and a buried heat source or tectonic triggering, both of which are non-controversial in Elysium's recent past. If our preferred interpretation is correct, this work would bolster the case for extremely recent and potentially shallow water in this region of Mars.
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